Apparatus whose output is a stack of sheets, for example, copiers and printers, commonly have the capability of providing that output in a variety of sizes. For example, modern copiers, copy onto ledger-sized sheets and feed those sheets longitudinally through a path which makes their in-track dimension approximately 17 inches. These same copiers feed letter-size sheets with the long dimension positioned across the path which makes their in-track dimension 8 1/2 inches. If letter-size sheets are fed into the usual downwardly slanted collection tray from an upper exit, and if that collection tray is long enough for ledger size sheets, the leading edge of such a letter-size sheet will engage the trailing edge of the stack and not slide down onto the top of the stack.
This problem has been corrected in the prior art by a number of mechanisms. For example, the exit from the paper path can be positioned at the bottom of the tray and sheets fed up the tray. Similarly, the tray itself can be made adjustable either manually or automatically by movement of a stop either up or down the receiving surface.
All geometries do not lend themselves to these solutions. For example, if the stack is being collected for finishing such as stapling, machine geometry may require the staple in the leading edge of the stack. In a bottom feed stacking arrangement, the trailing edge collects against a registration stop and the leading edge is up the tray at a location which varies according to sheet size. Either the stack or stapler must be movable to accommodate this geometry. Moving an unstapled stack is a difficult task.